Yes, it’s important to wash your hands. It’s critical during cold and flu season and especially if you visit someone at the hospital.

The problem is — in the West at least — parents have taken the business of keeping clean way too far.

New science shows that a lot of the tiny organisms called microbes that we’re so busy blasting away with our hand sanitizers, antibacterial soaps and liberal doses of antibiotics are having a profoundly negative impact on our kids’ immune systems, says microbiologist Marie-Claire Arrieta, co-author of a new book called Let Them Eat Dirt: Saving Our Children from an Oversanitized World.

The assistant professor at the University of Calgary, along with her co-author, esteemed microbiologist Brett Finlay, make the case that we’re raising our kids in a cleaner, more hyper-hygienic environment than ever before. They say that overdoing it the way we are is contributing to a host of chronic conditions ranging from allergies to obesity. I chatted with Arrieta recently to find out more.

What inspired you and Finlay to write Let Them Eat Dirt?

We’re both microbiologists and we’ve been studying the community of microbes that live in our guts — what we call our gut microbiome. In recent years research from our lab and other labs has shown that the health of this microbiome early in life is really crucial to our lifelong health. It’s not just that we’re scientists but we’re both parents. We thought that parents and caregivers would really benefit from us bringing this knowledge to the public.

We’ve been hearing for some time that overusing antibiotics may lead to antibiotic-resistant hospital infections, something we may associate with the elderly and other immune-compromised people. But I gather the implications are much more immediate and individual than that. What’s the connection between microbes and the development of the immune system in childhood?

When we’re born we do not have any microbes. Our immune system is underdeveloped. But as soon as microbes come into the picture, they kick-start our immune system to work properly. Without microbes our immune system can’t fight infections well.